The amylase inhibitors of wheat origin have been investigated (see, Phytochemistry, Vol. 20, No. 8, pp. 1781-1784; Eur. J. Blochem. 183, 37-40 (1989)).
U.S. Pat. No. 3,950,319 discloses that the amylase inhibitor extracted from wheat with water, an acid or an aqueous alcohol is used for the treatment of diabetes, obesity and the like.
The prior amylase inhibitors of wheat origin have not achieved such effect as expected when orally administered, which has the disadvantages of high cost and reduced inhibition of digestion to glucose, particularly for the digestion of heat cooked starch such as cooked rice.
Under such situation, a process has been sought of preparing in economy an amylase inhibitor which is effective in an oral administration for the digestion of heat cooked starch.
Japanese Patent Kokai Hei 5-301898 (corresponding to EPA 0567088 A2, Nisshin Flour Milling Co., Ltd.) discloses that the amylase inhibitors having a high amylase inhibitory activity but substantially no trypsin inhibitory activity can be produced by a process which comprises extracting wheat, wheat flour or wheat gluten with water, a dilute acid, a dilute alkali or an aqueous alcohol; adding a polysaccharide to an extract and separating the resultant insoluble complex from the solution; dissolving or dispersing said complex in a solution, then separating the polysaccharide from the solution to collect a solution containing the amylase inhibitor; and treating the collected solution with a cation exchanger to recover the amylase inhibitor from fractions that have not been adsorbed on the cation exchanger.